The present invention relates to a fusion welding apparatus for optical fibers used for permanently connecting optical fibers to each other.
As is common knowledge, fusion welding apparatuses for fusion welding optical fibers by making use of high frequencies and high voltage discharges are used and, in FIG. 6, an example of this type of fusion welding apparatuses for optical fibers is shown. As shown in the same figure, this type of fusion welding apparatus for optical fibers comprises a pair of discharge electrodes (discharge electrode rods) 1 for fusion welding optical fibers. In the apparatus illustrated in FIG. 6, the discharge electrodes 1 are retained by a U-shaped electrode retaining member 14 and discharge forming ends 5 on the tip ends of the discharge electrodes are arranged so as to oppose each other via a space. Between the discharge electrodes 1, a pair of optical fibers 2 are arranged so that connection end face sides thereof are opposed to each other, and which are arranged, for example, so that the optical axis of the optical fibers and the axis of the discharge electrodes 1 are roughly orthogonal to each other.
The optical fibers 2 are arrayed on the optical fiber arraying means 13 in a condition where sheathes on the tip end sides are removed and bare optical fibers 6 are exposed. On the surface of the optical fiber arraying means 13, V grooves 9 serving as optical fiber aligning grooves to insert the bare optical fibers 6 are formed. Herein, in the apparatus illustrated in FIG. 6, the optical fiber arraying means 13 are formed in the U-shape and the electrode retaining means 14 is fixed on a U-shaped concave portion 25 of the optical fiber arraying means 13.
Also, on the pair of discharge electrodes 1, a power source for discharge (not illustrated) is connected and by driving the power source for discharge, the connection end faces of the optical fibers 2 are fusion welded by discharge heat from the discharge electrodes 1.
Incidentally, in the abovementioned fusion welding apparatus for optical fibers, as shown in FIG. 7A, it is desirable that discharges A between the pair of electrodes 1 are stable, however, in actual fact, as shown in FIG. 7B and FIG. 7C, a phenomena where the discharges A sway and become unstable is recognized.
As a factor of the sway of the discharges A, the sway of the air due to the wind can be considered. In addition, as another factor of the sway of the discharges A, it is considered that electric field conditions surrounding the discharges change due to changes in the environment inside the fusion welding apparatus etc., thereby the location of the discharges is distorted or shifted. That is, in the fusion welding apparatus for optical fibers, for example, fusion mechanism portions such as an alignment mechanism (not illustrated) of the optical fibers 2 are provided, and it is considered that positions of these mechanism portions slightly change in each connecting operation and electric field conditions surrounding the discharges change due to subtle balance of an incorporated position of each portion of the fusion mechanism portion, thereby the location of the discharges is distorted and shifted.
Therefore, in order to prevent the discharges A from swaying under the influence of the wind, as shown in FIG. 8, a fusion welding apparatus for optical fibers which is provided with a windshield cover 12 for covering the connection end face sides of the optical fibers 2, discharge electrodes 1, optical fiber arraying means 13, and electrode retaining member 14 as a whole has been suggested.
Also, as shown in FIG. 9 and FIG. 10, fusion welding apparatuses for optical fibers which are provided with magnetic field control mechanisms for suppressing {compensating) the sway of the discharges A by controlling magnetic fields have been suggested. In the fusion welding apparatus for optical fibers as shown in FIG. 9, a coil 10 is wound around a magnetic core 23 for horizontal deflection and when a power source for discharge 8 is driven, a high frequency current is supplied with the coil 10, whereby magnetic fields are generated in a gap 24 of the magnetic core 23, thereby the sway of the discharges between the discharge electrodes 1 has been suppressed.
In the fusion welding apparatus for optical fibers as shown in FIG. 10, the magnetic core 23 and coil 10 for horizontal deflection are replaced with a magnetic core 23 and a coil 10 for vertical deflection, and by an effect similar to the case of FIG. 9, the sway of the discharges A is suppressed. Furthermore, in FIG. 9 and FIG. 10, 3 denotes a fiber cramp for cramping the optical fibers 2 and 16 denotes a driving unit.
However, as shown in FIG. 8, in the apparatus provided with the windshield cover 12, the sway of the discharges between the discharge electrodes 1 due to the wind can be suppressed, whereas the sway of the discharges between the discharge electrodes due to other factors cannot be suppressed, therefore, there have been many cases where the sway of the discharges between the discharge electrodes 1 cannot completely be suppressed. In addition, since such fusion welding apparatuses for optical fibers as described above are used for lay work of optical fibers, etc. to make the apparatuses lightweight and compact is demanded, however, in terms of the apparatuses shown in FIG. 9 and FIG. 10, there have been problems such that the apparatuses increase in size since the mechanisms for magnetic field control are provided and, moreover, the apparatuses have no practical use due to the large power consumption thereof.
The present invention is made for solving the above-described conventional problems as described above, and the object thereof is to provide a compact fusion welding apparatus for optical fibers which has a simple construction and which can stabilize discharges between discharge electrodes.
In order to achieve the above-described object, the present invention provides a fusion welding apparatus for optical fibers having the following construction. That is, a fusion welding apparatus for optical fibers according to the present invention is constructed so that a pair of discharge electrode tip ends, to which optical fibers are fusion welded, are arranged to oppose each other via a space, and connection end faces of a pair of optical fibers, which are arranged so that the connection end face sides thereof are opposed to each other between the discharge electrode tip end faces, are fusion welded by discharge heat from the discharge electrodes, wherein; dielectric bodies for suppressing the sway of discharges between the pair of discharge electrodes are provided.
Preferably, the dielectric bodies are provided along the longitudinal direction of the pair of discharge electrodes in a form so as to sandwich said pair of discharge electrodes from both sides thereof.
Furthermore, if necessary, in addition to providing the dielectric bodies, a windshield cover for covering, at least, a space between the discharge electrode tip ends and optical fiber connection end face sides is provided.
As an example mode of the present embodiment, the dielectric bodies are attached inside the windshield cover. And as a preferable example mode, the windshield cover is an open-and-close type cover which opens and closes by rotations around a spindle as its fulcrum and by a closing operation of the windshield cover, the pair of dielectric bodies are arranged along the longitudinal direction of the discharge electrodes at positions so as to sandwich said discharge electrodes from both sides thereof.
In the fusion welding apparatuses for optical fibers according to the present invention and prior art, electric fields as shown in FIG. 3A generate when a current flows between the pair of discharge electrodes arranged so that the tip ends oppose each other via the space. Namely an X axis shown in FIG. 3A corresponds to the axial center of the pair of discharge electrodes. When an axis which goes through the center between the discharge electrode tip ends and which is orthogonal to the X axis is provided as a Y axis so that space coordinates in terms of X and Y are formed, electric lines of force are shown by dashed lines while the equipotential lines are shown by solid lines in this space coordinates. Herein, q denotes a positive charge, xe2x88x92q denotes an negative charge, a position of the discharge forming end (tip end) of one of the pair of discharge electrodes is the position shown by q in the figure, and a position of the discharge forming end (tip end) of the other discharge electrode is the position shown by xe2x88x92q in the figure.
However, such electrical fields are changeable due to the above described changes in the environment inside the fusion welding apparatus and the electrical fields are unstable, therefore, it is considered that the discharges between the discharge electrodes sway when electric field conditions surrounding the discharge electrodes change.
Also, it is considered that the sway of the discharges also occurs, as described above, due to the sway of the air between the discharge electrodes.
With respect to problems, according to the present invention, the dielectric bodies (solid dielectrics) which suppress destabilization of the electric fields and the sway of the air at the same time and suppress the sway of the discharges between the pair of discharge electrodes, thereby enabling suppression of the sway of the discharges between the discharge electrodes, thus enabling stabilization of the discharges.
Hereinafter, the suppressive effects for the sway of the discharges between the discharge electrodes by means of the dielectric bodies will be described. Since dielectrics polarize when they are present in electric fields, for example, as shown in FIG. 3B, the dielectrics polarize when electric lines of force pass therethrough. Accordingly, in the electric fields as shown in FIG. 3A, when dielectric bodies 4 are provided along the longitudinal direction of discharge electrodes 1 in a form so as to sandwich discharge forming ends 5 of the discharge electrodes 1 from both sides thereof as shown in FIG. 2, the dielectric bodies 4 polarize as shown in FIG. 2 due to the electric lines of force shown by the dashed lines.
Thus, in the present invention, it is considered that the dielectric bodies polarize as described above, thereby enabling the provision of effects similar to those in a case where the vicinities of the dielectric electrodes are shielded, and thereby the electric field conditions in the vicinities of the discharges are allowed to lock, and therefore it is considered that the sway of the discharges caused by the sway of the electric fields can be suppressed.
Furthermore, by setting a distance L between the dielectric bodies (refer to FIG. 1) to the same degree as the distance between the discharge electrode tip ends or to a lower degree, the electric fields inside the dielectric bodies also take regulation effects and by adjusting the central position of the distance between the two dielectric bodies so as to coincide with the axial center of the dielectric electrodes, the discharges between the discharge electrodes are stably formed around the axial center of the discharge electrodes as shown in FIG. 7A.
Moreover, by providing the dielectric electrodes, the air around the dielectric electrodes decreases, whereby a flow of air between the discharge electrodes is suppressed accordingly and then, the sway of the discharges due to the sway of the air is suppressed. In particular, by setting the distance L between the dielectric bodies to 3 mm or less, occurrence of convection of the air which exists in the space between the dielectric bodies is significantly suppressed.
According to the above descriptions, in the present invention, the sway of the discharges between the pair of discharge electrodes is suppressed and the discharges between the discharge electrodes are stabilized. In particular, according to the present invention, for example, by providing the dielectric bodies along the longitudinal direction of the pair of discharge electrodes whose tip ends are arranged so as to oppose each other via the space in a form so as to sandwich the discharge electrodes from both sides thereof, electric fields which generate when a current flows can be stabilized by actions of the dielectric bodies.
Furthermore, since the dielectric bodies are provided, the air in the vicinity of the discharge forming portions of the discharge electrodes decreases, thereby the sway of the air between the discharge electrodes is suppressed. As a result, the sway of the discharges between the discharge electrodes is suppressed, thus the discharges are stabilized.
Also, in the present invention, by a simple composition, for example, such that the dielectric bodies are provided along the longitudinal direction of the pair of discharge electrodes in a form so as to sandwich said discharge electrodes from both sides thereof, stabilization of the discharges between the pair of discharge electrodes can be realized, therefore, no large-scale control mechanism such as a magnetic field control mechanism is necessary, and thus the apparatus can be made compact.
Furthermore, in terms of the apparatus wherein the windshield cover is provided, since the sway of the air between the dielectric electrodes due to the wind, etc. can be suppressed, the sway of the discharges between the dielectric electrodes can be suppressed more securely, thereby the discharge can be stabilized.
Furthermore, in terms of the apparatus wherein the dielectric bodies are attached inside the windshield cover, since the dielectric bodies can be arranged at appropriate positions in accordance with the opening and closing operations of the windshield cover, the arrangement operations of the dielectric bodies can be simplified.